%%
%% The LaTeX Companion, 3ed
%%
%% Example 6-7-12 on page I-483 in "dcolumn --- Decimal column alignments".
%%
%% Copyright (C) 2022 Frank Mittelbach
%%
%% It may be distributed and/or modified under the conditions
%% of the LaTeX Project Public License, either version 1.3c
%% of this license or (at your option) any later version.
%%
%% See https://www.latex-project.org/lppl.txt for details.
%%

\documentclass{tlc3exa}
\pagestyle{empty}
\setcounter{page}{6}
\setlength\textwidth{207.0pt}
%StartShownPreambleCommands
\usepackage{dcolumn}
%StopShownPreambleCommands

\begin{document}
\begin{tabular}{|D..{-1}|D..{2}|D..{4.2}|}
  \multicolumn{1}{|c|}{wide heading} &
  \multicolumn{1} {c|}{wide heading} &
  \multicolumn{1} {c|}{wide heading}
                                  \\[3pt]
 1000.20  & 1000.20  & 1000.20    \\
  123.45  &  123.45  &  123.45    \\
  12.345  &  12.345  &  12.345    \\
   -1.23  &   -1.23  &   -1.23
\end{tabular}
\end{document}
